Really, really ballsy move. I definitely wouldn't have done it if I were them. If I've learned one thing through experiences with other musicians (auditions or whatever), I've realized that the world is full of musicians who love to brag that they can play, but really actually suck. I wouldn't be willing to take a chance like that.

Nevertheless: That's fucking badass for that kid. I'd be dying if that happened to me.

In Flames did something similar to this in 08 at a Gigantour off-date show with Children of Bodom in Philly. I think in that case, the kid won some sort of contest but he got up on stage and played Jotun with them and nailed it. This is also nice cause I got to hear Jotun, which they rarely play now-a-days...